LIMA/SAO PAULO (Reuters) – Peru’s chances of qualifying for the World Cup for the first time since 1982 dimmed on Friday after soccer’s governing body FIFA suspended the team’s captain Paolo Guerrero for failing a doping test.

Unless reversed, the 30-day provisional suspension will deprive Peru of its main striker for two playoff matches against New Zealand this month to determine which team will play in the World Cup in Russia next year.

The substance found in the exam was a stimulant and Guerrero must now demonstrate where it came from, FIFA anti-doping official Fernando Solera told ESPN Brazil. “For the FIFA disciplinary committee and for us working in the area of doping control, there is no doubt at all that a banned substance was present,” Solera said in the broadcast interview.

Guerrero, 33, could not be reached for comment. His mother, Petronila Gonzales, urged Peruvian fans to have faith in him and suggested cold medication might have been detected in the exam.

“Paolo had a terrible cold” when he was tested after an Oct. 5 match against Argentina, Gonzales told journalists. “This will be over in 30 days and you’ll see. He’s an exemplary man.”

With Guerrero as captain and Argentine Ricardo Gareca as coach, Peru has come closer to qualifying for the World Cup this year than it has in decades – helping to boost the approval rating of President Pedro Pablo Kuczynski.

Guerrero, a striker for the Flamengo sports club, has scored 32 goals in 83 internationals. His free kick goal against Colombia in the final qualifier in October helped Peru get the point that guaranteed them a playoff spot.

The Peruvian Football Federation, which announced FIFA’s decision to suspend Guerrero on Twitter, said it hoped the results of the test would be cleared up soon.

Peru will play New Zealand in Wellington on Nov. 11 with the return leg four days later in Lima.

The suspension also means Guerrero will miss the semi-final of the Copa Sudamericana, South America’s equivalent of the Europa League. Flamengo will play Colombian side Junior Nov. 23 in Rio de Janeiro before heading to Baranquilla for the return leg a week later.

Flamengo said Guerrero always had exemplary professional conduct and will not play in a match against the Gremio soccer club on Sunday for the Brazilian championship.

(Reporting by Mitra Taj and Teresa Cespedes in Lima and Andrew Downie in Sao Paulo; Editing by Pritha Sarkar and Lisa Shumaker)